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Add the dependencies to your project:

implementation 'com.snakydesign.livedataextensions:lives:1.2.1'
implementation 'android.arch.lifecycle:extensions:x.x.x' // If you are using the AndroidX version, that's fine too, as the Jetifier will take care of the conversion.

If you want to use this library on a Java project, add the following dependency:

implementation 'org.jetbrains.kotlin:kotlin-stdlib:x.x.x'

Usage

Kotlin

Import the functions

import com.snakydesign.livedataextensions.*

Creating LiveData

liveDataOf : Create a LiveData object from a value (like just in RxJava, although it immediately emits the value)

take(n:Int) : produces a LiveData that produces only the first n Items.

takeUntil(predicate) : Takes until a certain predicate is met, and does not emit anything after that, whatever the value.

skip(n) : Skips the first n values.

skipUntil(predicate) : Skips all values until a certain predicate is met (the item that actives the predicate is also emitted).

elementAt(index) : emits the item that was emitted at index position

nonNull() : Will never emit the nulls to the observers (outputs a NonNullLiveData).

defaultIfNull(value): Will produce the value when null is recieved.

Combining

merge(List<LiveData>) : Merges multiple LiveData, and emits any item that was emitted by any of them

LiveData.merge(LiveData) : Merges this LiveData with another one, and emits any item that was emitted by any of them

concat(LiveData...) : Concats multiple LiveData objects (and converts them to SingleLiveData if necessary, and emits their first item in order. (Please check the note below.)

LiveData.then(LiveData) : Concats the first LiveData with the given one. (Please check the note below.)

LiveData.merge(LiveData) : Merges this LiveData with another one, and emits any item that was emitted by any of them

startWith(startingValue): Emits the startingValue before any other value.

zip(firstLiveData, secondLiveData, zipFunction): zips both of the LiveDatas using the zipFunction and emits a value after both of them have emitted their values, after that, emits values whenever any of them emits a value.

combineLatest(firstLiveData, secondLiveData, combineFunction): combines both of the LiveDatas using the combineFunction and emits a value after any of them have emitted a value.

LiveData.sampleWith(otherLiveData): Samples the current live data with other live data, resulting in a live data that emits the last value emitted by the original live data (if any) whenever the other live data emits

Transforming

map(mapperFunction) : Map each value emitted to another value (and type) with the given function

switchMap(mapperFunction) : Maps any values that were emitted by the LiveData to the given function that produces another LiveData

doBeforeNext(OnNextAction) : Does the onNext function before everything actually emitting the item to the observers

doAfterNext(OnNextAction) : Does the onNext function after emitting the item to the observers(function) : Does the onNext function before everything actually emitting the item to the observers

buffer(count) : Buffers the items emitted by the LiveData, and emits them when they reach the count as a List.

scan(accumulator) : Applies the accumulator function to each emitted item, starting with the second emitted item. Initial value of the accumulator is the first item.

scan(seed, accumulator) : Applies the accumulator function to each emitted item, starting with the initial seed.

amb(LiveData...) : Emits the items of the first LiveData that emits the item. Items of other LiveDatas will never be emitted and are not considered.

toMutableLiveData() : Converts a LiveData to a MutableLiveData with the initial value set by this LiveData's value

Java

You can call any function prefixed with Lives keyword.

import com.snakydesign.livedataextensions.Lives;

Example (create a LiveData with the initial value of 2 and map each value to its String type

Notes

Please note that because of design of LiveData, after a value is emitted to an observer, and then another value is emitted, the old value is destroyed in any LiveData object. So unlike RxJava, if a new Observer is attached, It will only receive the most recent value.

So If you want to use operators like concat, you have to consider allowing only one observer to the LiveData.

PRs are more than welcome, and please file an issue If you encounter something 🍻.

License

Copyright 2018 Adib Faramarzi.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.